Balloon catheter technology makes use of balloons of fixed lengths, whereby the great number of medical procedures requiring balloon catheter technology makes it necessary to rely on several catheters of different balloon length. When a procedure requires, for example, two differently sized balloons, it is necessary to change balloon catheters or to act sequentially with the one length balloon available. Changing balloon catheter is costly while sequential action with the available balloon length may be a time-consuming and potentially hazardous procedure which may lead to injury of the patient or insufficient dilatations.
The balloon catheter is also an instrument of common use as a mechanism for transporting and applying a balloon expandable prosthesis, called a stent, for maintaining the patency of a vessel. The length of the balloon must be chosen as a function of the length of the stent, to avoid inappropriate expansion of the stent or damage to the vessel. This may also lead to the costly need of a plurality of balloon catheters to correctly and safety apply the stents.
U.S. Pat. No. 5,246,421 refers to a method of treating obstructed regions of bodily passages which provides for use of balloon catheters with adjustable length balloons. Accordingly, this document teaches the use of a balloon catheter in which an adjustable sheath is externally manipulated to partially surround and contain the dilatation balloon segment of the catheter in situ during a treatment procedure. By external manipulations sliding the sheath forwardly and backwardly to expose a predetermined length of the balloon segment prior to inflating the balloon, various balloon lengths can be obtained. The catheter body can comprise an elongated tube and a balloon attached by both its neck portions to two axially spaced locations on the elongated tube; the catheter can also have a catheter body defining a lumen with a balloon terminating such a body as an integral one piece assembly having a closed end. The document outlines that the described technology can be modified or tuned to be compatible with virtually any catheter constructions, including over the wire catheters and fixed wire catheters. In order to avoid creep of the sheath during or after inflation of the balloon tending to encover more balloon than originally selected, the position of the sheath may be firmly fixed, for example by a clamping device, prior to inflation of the balloon. The mere fact that the sheath is externally manipulated creates a substantial complication in the catheter construction, and the risk of having the sheath clogged up. In addition, the system is relatively cumbersome and rigid due to the multiplicity of elements resulting from the externally manipulated sheath over the catheter shaft, which may cause some difficulties for the treatment of tortuous or narrow vessels. And there may also be a friction problem between the sheath and catheter shaft which may add difficulties to the external manipulation of the sheath. There is no suggestion in this document that the moving sheath and resulting variable length balloon catheter could be envisaged as a system for matching the balloon length requirements for stent delivery.
European Patent Application No. 94118900.3 filed Nov. 30, 1994 by an applicant of the present invention shows a balloon catheter as described hereinbefore in which the tubular shaft comprises a guidewire lumen with an entry for the guidewire distal of the balloon and an exit for the guidewire distal of the proximal end of the tubular shaft, and means for preventing expansion of balloon segments comprising a not distensible sleeve attached to the tubular shaft either distal of the exit for the guidewire if said exit is proximal of the balloon or proximal of the exit for the guidewire if said exit is distal of the balloon. This document also shows a stent delivery system for a balloon expandable stent comprising a balloon catheter having the features as described hereabove. This development is specifically directed to modification of the length of the balloon in balloon catheters and stent delivery systems which make use of the fast and efficient technology known under the name MONORAIL.RTM..
All documents cited herein, including the foregoing, are incorporated herein in their entireties for all purposes.
It is an object of this invention to further improve over the prior at by proposing a balloon catheter which is highly versatile and efficient, simple to manufacture, and easy and safe to use. A further object of the invention is to propose a stent delivery system which is also versatile and efficient, which is simple to manufacture, and which is easy and safe to operate. To this effect, the invention complies with the definitions given in the claims.